Temperaturen blir lavere om natten.

Because Norwegian usually puts the definite article at the end of the noun.

• en temperatur = a temperature
• temperaturen = the temperature

So temperaturen is the definite form, meaning the temperature.

This is very common in Norwegian:

• en bil → bilen
• en dag → dagen
• et hus → huset

Blir is used because it shows change: the temperature becomes / gets lower.

• Temperaturen blir lavere = the temperature gets lower
• Temperaturen er lavere = the temperature is lower

So blir focuses on a change happening, not just a static condition.

Lavere is the comparative form of lav.

• lav = low
• lavere = lower

In Norwegian, many adjectives form the comparative by adding -ere:

• stor → større
• kald → kaldere / often kaldere in regular formation, though other patterns exist with some adjectives
• lav → lavere

So blir lavere means gets lower.

Because the comparison is understood from context.

In English, you can also say The temperature gets lower at night without explicitly saying than during the day. Norwegian works the same way.

If you want to make the comparison explicit, you can add enn:

• Temperaturen blir lavere om natten enn om dagen.

Here, enn means than.

Om natten is a common time expression meaning at night or during the night.

Here, om is being used in a time sense, not in the sense of about or if.

The form natten is definite, and that is normal in this kind of expression. Norwegian often uses the definite form in set time phrases:

• om dagen = during the day / by day
• om kvelden = in the evening
• om natten = at night

So this is something you should mostly learn as a fixed expression.

Yes, absolutely.

Both are correct:

• Temperaturen blir lavere om natten.
• Om natten blir temperaturen lavere.

When you move om natten to the front, the verb blir still has to stay in second position. That is a very important rule in Norwegian main clauses, often called the V2 rule.

So:

• Om natten
  • blir
    • temperaturen
      • lavere

Not:

• Om natten temperaturen blir lavere ❌

Because lavere is being used predicatively after blir, and comparative adjectives normally do not change for gender or number in this use.

Compare:

• Temperaturen blir lavere
• Prisene blir lavere
• Huset blir lavere

The form lavere stays the same.

So even though Norwegian adjectives often agree with nouns in some situations, the comparative form used after verbs like er and blir is usually unchanged.

Bli is a very common Norwegian verb meaning become, get, or sometimes come to be, depending on context.

In this sentence:

• blir is the present tense of bli

Basic forms:

• å bli = to become / to get
• blir = becomes / gets
• ble = became / got
• blitt = become / gotten

You will see bli in many everyday sentences:

• Det blir mørkt. = It gets dark.
• Jeg blir trøtt. = I get tired.
• Det blir bedre. = It gets better.

So this sentence is a very typical use of bli.